Color stable ketone solvent composition



3,345,504 Patented Sept. 12, 1967 3,341,604 COLOR STABLE KETONE SOLVENT COMPOSITION Joseph R. Quelly, Fanwood, N.J., assigner to Esso Reing calculated as acetic acid. Standard alkali titration techniques are employed to determine this acid number. Other processes for the production of ketones may lead to a product contaminated with impurities which will 5 render the product subject to degradation. gg g f Engineering Company a cerporanon of Despite the high purity product which is obtained by No Drawing Filed Jam 23, 1963 Set. No. 254,500 extensive and elaborate fractionation techniques, it has 4 C] i (g g60. 593 been found that storage of the high purity ketone results in the formation frequently of color bodies such as yel- This invention relates to the stabilization of lower allow, amber, green and brown. These color bodies cause kyl ketones. In particular this invention relates to novel the specified water white liquid product to assume usucompositions of matter comprising a lower alkyl ketone ally a yellow color. Since discolored ketones are objeccontaining stabilizing amounts of ascorbic acid. Still more tionable to the consumer such discolored products would spec'ically in a preferred embodiment this invention renormally require extensive refinishing techniques before lates to the stabilization of methyl ethyl ketone obtained they could be sold. It has now been found that the acid by catalytic dehydrogenation of secondary alcohols, or number also often increases in storage to a point where in general ketones prepared by other means containing it no longer meets specification. This also requires excontaminants similar to those contained in ketones pretensive and costly refinishing steps. The particular mechpared by catalytic dehydrogenation processes. anism for this degradation of product and/or increase Lower dialkyl ketones containing from 3 to 8 carbon of acidity is not known; however, it is believed that the atoms per alkyl group in accordance with one commerparticular contaminants present in the high purity ketone cial method are prepared by the catalytic dehydro'genacatalyze in the presence of air the formation of diketones, tion of secondary alcohols. For example, methyl ethyl e.g., 2,3-butanedione by oxidation of the high purity prodketone may be produced by subjecting secondary butyl uct ketone itself. This is extremely surprising in that text alcohol to temperatures of 600960 F. in the presence books on organic chemistry are in agreement to the efof a Group II metal oxide preferably supported on a carfeet that ketones are relatively stable towards oxidizing rier. Other catalysts are also known to effect this reacagents and in fact they will not reduce ammoniacal siltion. Also, other dialkyl ketones may be produced by rever nitrates, gold salts or Fehlings solution. The degraacting corresponding secondary alcohols such as hexadation product formed on storage is ordinarily higher no1-2 which may be converted to methyl butyl ketone, boiling than the ketone and can be separated from the pentanol-2 to methyl propyl ketone, pentanol-3 to diethyl ketone by fractional distillation. Obviously, the cost of ketone, etc. In commercialmanufacturing plants the crude the fractional distillation plus the cost of the product product as it comes from the dehydrogenation unit comlost, e.g. up to about 10% bottoms, makes it especially prises major amounts of the desired ketone with minor desirous to avoid the formation of degradation product amounts of the unreacted feed and byproduct contamiand to promote stabilization of the ketone. It is further nants such as other lower molecular weight ketones and/ believed that the contamination is also probably promoted or alcohols resulting from a certain degree of cracking by external contaminants introduced from the transporwithin the reaction vessel. Water may also be present in tation and storage facilities, e.g. chloride and iron salts. the crude reaction mixture. The ketone is then fraction- In any event it is not intended to limit this invention by ally distilled to obtain a substantially pure product. Vari- 0 any theory of the mechanism involved, the surprising and ous techniques for fractional distillation are employed ineffective improvement obtained being the invention now cluding the use of water which aids in the separation of taught. the ketone from the corresponding alcohol. When water For a better understanding of the invention, reference is employed in substantial amounts the process is deis now had to Table I which sets forth the acidity and scribed as an extractive distillation which, for example, color of several different large samples of methyl ethyl may result in recovering the aqueous unreacted alcohol ketone before and after storage. It will be noted from as a bottoms extract and the relatively pure ketone as the table that the original acidity is less than about 0.002 an overhead raflinate from the extractive distillation unit. and the original color approximately 0-5 Hazen. The The particular manner in which the ketone is purified is acidity and color increased substantially on storage over not important to the successful operation of the present 2 and 4 month periods.

TABLE I.STORAGE STABILITY OF M.E.K.

Original After Storage Sample Time of Storage Acidity Color Acidity Color 0.001 0 2mos. (approx) (Jan.-l\ia1'ch) 0. 0061 30 0.0016 5 2mos. (April-June) 0. 037 10 0.001 0 4mos. (July-November) 0.013 15 invention. Ketones are, however, well known commercial solvents which in accordance with consumer must have an extremely high purity. Typical minimum specification for methyl ethyl ketone will run about 99.4%. In order to meet the standards required, these ketones must be substantially colorless, i.e., water white, and have a low acid number of, for example, 0.002. The term acid number as employed herein refers to grams of acid per hundred grams of sample, the acid bedemand ketones, reference To further demonstrate the instability of high purity may be had to the following table which shows the results of an accelerated storage test on methyl ethyl ketone. It will be noted from the table that the original high purity product employed had an acid number below the specification maximum. The increase in acidity by air blowing in an accelerated storage test is shown. After only 7 hours the previously pure ketone contained an acid number which is unacceptable 4- to the trade for many purposes, a ketone product which acid, sodium nitrite, Sustane, Dupont Metal Deactimust be rerun at considerable expense to the manufacturvator, or Tenarnene-Z produce foreign color in MEK, er. and saccharin and triphenyl phosphite were completely ineifective. It is apparent therefore that the commercial anti-oxidants tried actually worsened both the acidity and color over the unstabilized control treated by re- TABLE II.ACCELERATED STORAGE 'rns'rs fluxing with air over a similar period of time.

In accordance with this invention it has been found Sample No. Time (With Air) Acid Number that ascorbic acid has an unexpected stabilization effect on lower alkyl ketoues when added in very small parts 0 0 019 per million. The amount added may be .0001 to 1 wt. 818% percent, preferably 50 to 100 ppm, more preferably 5 33 .5 to 30 ppm.

The present invention will be more clearly understood from a consideration of the following examples presenting data obtained in the. laboratory and in the field.

EXAMPLE 1 Ascorbic acid was tested and found to be efiective in stabilizing methyl ethyl ketone (MEK) in an accelerated storage test.

The accelerated storage test is efiected by boiling methyl ethyl ketone under reflux and at the same time bubbling air through the ketone for the number of hours set forth above at a rate of about 0.5 cubic ft./hr.

To demonstrate the effect of storage on color, a portion of ketone having the acidity of Sample A in Table I was subjected to the accelerated storage test and the color was determined after 2, 4, and 20 hours. Initial TABLE IV color on a Hazen scale was 0-5 or substantially water white. After 2 hours of refluxing with bubbled air, the AMT 1gtateof1 color formed with a Hazen rating of 10; after 4 hours 1 iaceiy Addt c F t the color had a Hazen rating of and after 20 hours 1 we one p p m r e r e ni tii the product turned greenish. Reference is now had to Reference Table III which shows a relationship between acidity and colon Ascorbic acid 20 15 None (reference 100 Ascorbic acid 10 41 None (reference) 1 100 TABLE III 1 Reference MEK product tested was color-unstable material taken from Tank 57 at Good Hope, La, in September. Tests were made at 80 C. for 16 hours under 10 p.s.i.g. oxygen pressure in the presence of Sample Time of Heating Color 1 Acidity tank-steel test piece (air) (hours) 2 Added as aqueous solution, .01 vol. percent on MEK.

EXAMPLE 2 1 Estimated Hazen ratings. The Hazen color scale is not an especially 4:5 A bi id was d to t bili h l th l k t good technique for measuring color of stored methyl ethyl ketone. The

eyet $31 33011 131? difierenciefs 1:1 easily than the coogmetpg tlvlgn and was found not to harm routine inspections of he me y e y 'e one goes 0 no or in s orage as measure y 9.2! l y. e r

Hazen colors are no match. Sometimes they have a green cast, at product m tests shown bfilow' other times yellow, brownish, etc. and the colorimeter cannot measure these differences. The color is therefore only an estimate and is not int pd d to fl c a true az rating- TABLE V.-ROUTINE INSPECTION CHARACTERISTIC Green- OF MEK PRODUCT ARE NOT HARMED SIGNIFIGANTLY BY ADDITIVES Additive 1 Typical To combat this apparent degradation by. oxidation of Inspection 'f g ketones in storage, a number of known anti-oxidant- None Alicqgbzlc piclficastabilizers were added in amounts which would normally be sufiicient to stabilize an organic compound from oxida- M u l I c e v i a t on. These inhibitors include Sustane, 1.e., butyl hydroxy 0 0 0 5% anisole (C11H1602), tocopherol, i.e. vitamin E (C H O T n,

Initial 79. 2 7a. 2 4 7s. 6 and tertiary butyl catechol (C H O A sample of 0 Dry Point 79,7 9,7 80,6 h h t 1 f i an n Sp. Gravity, 20/20 0 0.8060 0.8060 0805 0.807 et yl k6 one 1 g a C0 or ratnlg o 0 d a Nonvolatile-Matter,gram/1001111.. 0.0002 0.0004 0.002 acidity of 0.0004 was employed. The control was refluxed Purity, as MEK Wt percent 4 3 with air as described previously with a resulting increase Water content, Percent [104 in color to 5 and 10 after 7 and 14 hours and an increase 1 1 Concentration of additive, 10 ppm. by wt. 1n acidity to 0.0014 after 7 hours, and to 0 0120 after 14 5 2 A a de a (as aqueous Solution, .01 S0111 tion in MEK' hours. With Sustane after 7 hours the acidity was 0.0024 3 Max and the color was 50. With tocopherol the color was 30 4 and the acidity was above specification. With tertiary butyl catechol the color was also 30 and the acidity was up EXAMPLE 3 to 0.020. Other substance with poor inhibitory action are secondary and tertiary alcohols; water, and acetaldehyde T ex ple p e e s r s lts O tained in stabilizing had some butnot outstanding inhibitory action. Sodium methy isobutyl ketone With ascorbic acid in the, diethyldithiocarbamate and aluminum coupled to iron presence also of contaminants which accelerate the formawere inhibitors under certain conditions, 'but reproducible tion of impurities. The commercial MIBKused was preresults could not be obtained. Propyl gallate, phosphoric pared by the normal process of condensation of acetone to mesityl oxide followed by hydrogenation to MIBK and had a purity of above 99%.

It is to be understood that this invention is not limited to the specific examples which have been ofiered merely TABLE VI.PEROXIDATION OF MIBK IS OATALYZED BY DISSOLVED CHLORINE AND IRON IN THE PRESENCE OF STEEL, B UT INHIBITED BY ASCO RBIC ACID Contaminants Added, Rate of Rate of p.p.m. Peroxidation, Inhibitor Metal Diketone p.p.m. act. Added 3 Present 3 Formation, per day 1 p.p.m. per Chloride Iron day 4 0.0 0. 0 8. 5 None Rusty steel 1. 5 0. 0 21 one 14 1.5 0.0 26 Clean zinc. 18

1. 5 0. 0 43 Rusty steeL 90 1. 5 0. 0 48 Clean steel 21 1. 5 0. 0 144 Rusty steel- 58 1. 3 0.7 Clean zinc 77 l. 3 0. 7 28 Rusty steel- 49 1.3 0.7 137 None do 86 1 50 ml. commercial MIBK, lots designation B, subjected to heating in an ASTM-D 525 glass-lined bomb at 80 accelerated storage test 0. for 22-114 hours under 10 p.s.i.g.

initial oxygen pressure. Increase in peroxide content determined by conventional analysis.

2 Inhibitor concentration was 0.001% when added. 3 Metal test piece was Iii-gauge, 0.125 x 0.125 inch in size.

4 Increase in diketone content (yellow color body) during test determined spectrophotometrically.

EXAMPLE 4 The data presented below present an actual storage test showing the effect of adding ascorbic acid with also data on the amount of peroxides and acidity formed. TABLE VIL-DISCOLORATION AND PEROXIDATION 0F AIR-SATURATED MIBK EFFECTIVELY INHIBIIED DUR- ING STORAGE AI 104 F. IN

1 Diketone is yellow color body formed by autooxidation and is determined spectrophotometrically.

2 Special yellow value is spectrophotometric interpolation of ASTM Platimim-Cgbalt color. Maximum color current specified for MIBK produc is 1..

as illustrations and that modifications may be made without departing from the spirit of the invention.

What is claimed is:

1. A dialkyl ketone of 3 to 8 carbon atoms stabilized with 0.0001 to 0.5 wt. percent of ascorbic acid.

2. Methyl ethyl ketone stabilized With 0.0001 to 0.5 wt. percent of ascorbic acid.

3. Methyl isobutyl ketone stabilized with 0.0001 to 0.5 wt. percent of ascorbic acid.

4. Methyl isobutyl ketone stabilized with 5 to 25 ppm. of ascorbic acid.

References Cited UNITED STATES PATENTS 2,212,831 8/1940 Hotfmann et a1 167-81 2,269,145 1/1942' Culter et al 16781 2,377,188 5/1945 Schwenk et a1. 260-621 2,868,691 1/1959 Porush et a1. 16781 2,928,767 3/1960 Gulesich et al 167-81 OTHER REFERENCES Merck Index, 7th edition, p. 106 (1960), Merck and Co., publishers.

LEON ZITVER, Primary Examiner. D. HORWITZ, Assistant Examiner. 

1. A DIALKYL KETONE OF3 TO 8 CARBON ATOMS STABILIZED WITH 0.0001 TO 0.5 WT. PERCENT OF ASCORBIC ACID. 